Re: [v6ops] new draft: draft-taylor-v6ops-fragdrop

["Templin, Fred L" <[e-mail]>]

You know, all of this discussion is moot. RFC2460, Section 5 says:

   "In order to send a packet larger than a path's MTU, a node may use
   the IPv6 Fragment header to fragment the packet at the source and
   have it reassembled at the destination(s).  However, the use of such
   fragmentation is discouraged in any application that is able to
   adjust its packets to fit the measured path MTU (i.e., down to 1280
   octets).

   A node must be able to accept a fragmented packet that, after
   reassembly, is as large as 1500 octets.  A node is permitted to
   accept fragmented packets that reassemble to more than 1500 octets.
   An upper-layer protocol or application that depends on IPv6
   fragmentation to send packets larger than the MTU of a path should
   not send packets larger than 1500 octets unless it has assurance that
   the destination is capable of reassembling packets of that larger
   size."

That means that a source node has every reason to expect that, if
it fragments a packet that is no larger than 1500 bytes, then the
destination will be able to reassemble it. Host fragmentation is
therefore an integral part of correct IPv6 operation, and that's
the law until someone writes a different one. Middleboxes therefore
have no basis for dropping fragments, unless they can through some
means be determined as malicious (e.g., VFR).

Thanks - Fred
[e-mail]